Can a book this long awaited also be unexpected? Stephen Harper’s first book is. A Great Game: The Forgotten Leafs & The Rise of Professional Hockey is billed as a look at the early history of the sport. It’s being marketed as a tale for hockey obsessives. But what it is, really, is something better and more interesting and, from the perspective of book sellers, probably less saleable: a history of Canada in the early years of the last century, before the old world was washed away by The Great War.

The entry into that world comes through the tale of Toronto’s earliest professional hockey teams. Between 1908 and 1914, they challenged for the Stanley Cup. They did so while fighting a far more vicious battle off the ice: against Toronto’s conservative hockey establishment, which sought to destroy any club or player committing the original sin – playing the game for money.

Mr. Harper’s book reads a bit like a PhD thesis, which is to say that it is well researched, and sometimes heavy going. He seems to be aiming to write the definitive take on these events, so minor details aren’t left out. The pacing of the narrative sometimes suffers. But the Prime Minister does a good job of taking you back to the country, and the time, that gave birth to the national game.

The Canada of 100 years ago is in some ways easily recognizable to us: immigrants arrived in record numbers, the cities boomed and hockey was already incredibly popular, with the Stanley Cup already the ultimate prize. Players wanting to make their fortune headed south: After he and his teammates in Berlin (now Kitchener, Ont.) were suspended for accepting a gift of $10 gold coins from the city’s mayor, John “Doc” Gibson moved to northern Michigan and created what appears to have been North America’s first openly professional hockey team, in 1903.

There were debates over hockey violence, and counterclaims that new rules were robbing the game of its manly nature. In 1904, the Belleville Intelligencer accused the authorities of turning hockey into a wimpy “cross between croquet and ping-pong.” It sounds like a quote from Coach’s Corner.

But in other ways the Canada that is the setting for A Great Game is now a foreign country. Toronto before the First World War was run by people who saw themselves as defenders of the British heart of a British Canada. Mr. Harper describes them as so conservative that they remained stuck in the Victorian era long after it had ended, and he contrasts them with the “palpably more flexible” elites of Montreal.

The differences of opinion about the national character went to the heart of the rules of the national game. The Montreal-based Amateur Athletic Federation of Canada simply looked the other way as top-level hockey evolved into a professional sport. The Toronto-based Ontario Hockey Association, in contrast, was puritanical in its zeal to eliminate professionalism. Professionalism was vice.

John Ross Robertson, the publisher of the Telegram newspaper, and iron-fisted head of the OHA, said that professionalism was a violation of “the ideals which are part of our birthright as Canadian sons of the greatest of countries, and as British citizens of the grandest of empires.” The battle wasn’t just about hockey.

But it was also about hockey. The Stanley Cup had been around since 1893, and it had never been won by a Toronto team. (Does nothing change?) Toronto badly wanted a Cup. The people running hockey in Toronto – the conflict-of-interest-ridden board of the OHA included editors from the Toronto Star, the Telegram and The Globe – also wanted to win on their own terms. That meant amateurs only. But as the rest of the country went professional, some Torontonians followed the lead, setting up a pro team known as the Toronto Hockey Club. They played their first game in December, 1906. A war for the soul of hockey was on.

We know how it ended. Forbes magazine now perennially ranks the Toronto Maple Leafs as the world’s most valuable hockey franchise. And the Leafs can trace their origins right back to that first rebel club that dared to go pro more than a century ago.